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PREFERRED AND ENERGETICALLY OPTIMAL TRANSITION SPEEDS DURING BACKWARD
HUMAN LOCOMOTION
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Alan
Hreljac ,
Rodney Imamura, Rafael F. Escamilla, Jeffrey Casebolt and Mitell Sison |
Department of Kinesiology and Health Science, California State University,
Sacramento, CA, USA
| Received |
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03 May 2005 |
| Accepted |
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12
September 2005 |
| Published |
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01
December 2005 |
©
Journal of Sports Science and Medicine (2005) 4, 446
- 454
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| ABSTRACT |
| Some
aspects of backward locomotion are similar to forward locomotion,
while other aspects are not related to their forward counterpart.
The backward preferred transition speed (BPTS) has never been directly
compared to the energetically optimal transition speed (EOTS), nor
has it been compared to the preferred transition speed (PTS) during
forward locomotion. The purpose of this study was to determine whether
the BPTS occurs at the EOTS, and to examine the relationship between
the backward and forward preferred gait transition speeds. The preferred
backward and forward transition speeds of 12 healthy, young subjects
(7 males, 5 females) were determined after subjects were familiarized
with forward and backward treadmill locomotion. On a subsequent day,
subjects walked backward at speeds of 70, 80, 90, 100, and 110% of
the BPTS and ran backward at speeds of 60, 75, 90, 100, and 120% of
the BPTS while VO2 and RPE data were collected. After subtracting
standing VO2, exercise VO2 was normalized to
body mass and speed. For each subject, energy-speed curves for walking
and running were fit to the normalized data points. The intersection
of these curves was defined as the EOTS which was compared to the
BPTS using a paired t-test (p < 0.05). RPE and VO2 at
the BPTS were also compared between walking and running conditions,
and the correlation between BPTS and PTS was calculated. The EOTS
(1.85 ± 0.09 m·s-1) was significantly greater than the
BPTS (1.63 ± 0.11 m·s-1). Even though RPE was equal for
walking and running at the BPTS, VO2 was significantly
greater when running. There was a strong correlation (r = 0.82) between
the BPTS and the PTS. Similar to forward locomotion, the determinants
of the BPTS must include factors other than metabolic energy. The
gait transition during backward locomotion exhibits several similarities
to its forward counterpart.
KEY
WORDS: Running, walking, gait transition, preferred transition
speed.
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